How to add some data input in a CNN?
If your interest is positional information, encode it!

This could include learning an embedding for each position and leveraging that in your model. You could also use an approach to hard-encode rather than learn it (kinda like adding sinusoids in the transformer paper Attention is All You Need

an example of a paper that encodes the 2D positional info: Attention Augmented Convolutional Networks